Herrick Laboratories at Purdue University.

Ways to make CO₂ viable comprised several papers presented at concurrent refrigeration, natural working fluids, and compressor conferences held here.

And attendees were given a tour of the university’s Herrick Laboratories, where several CO₂ experiments were taking place.

Researchers reported making progress in perfecting automotive and portable air conditioning equipment that uses CO₂. They noted a resurgence of interest because it is a natural refrigerant that does not have the global warming potential of artificially made HFCs. They also said they have seen favorable technological advances that include the manufacture of extremely thin yet strong aluminum tubing.

In the reports and in the lab were:

• Creation of the first computer model that simulates the performance of carbon dioxide-based air conditioners;

• The design of a portable, CO₂-based air conditioner that works as well in conventional military applications, researchers said;

• The development of a mathematical correlation, a tool that will enable engineers to determine how large a heat exchanger is needed to provide cooling for a given area; and

• Development of a method to predict the effects of lubricating oils on the changing pressure inside CO₂ air conditioners.

Researchers commented that, “Carbon dioxide is promising for systems that must be small and lightweight. Various factors, including the high operating pressure required for CO₂ systems, enable refrigerant to flow through small-diameter tubing, which allows engineers to design more compact air conditioners.”

Researchers also argued that the naturally produced CO₂ would not be subject to the recovery regulations governing CFCs, HCFCs, and HFCs.

They further noted that HFCs have 1,400 times more global warming potential than CO₂, and that CO₂ can be garnered from non-hvacr processing.

According to Purdue’s Eckhard Groll, “It was actually very heavily used as a refrigerant in such spaces as theaters and restaurants in the early 20th century,” but at the time it required heavy steel tubing. “But now extremely thin, yet strong, aluminum tubing can be manufactured.”

At present, Groll noted that CO₂ has no advantage in larger air conditioners, which can use wide-diameter tubes. But he said ammonia, another natural refrigerant, is being looked at in more commercial refrigeration applications.

Publication date: 08/21/2000